The 10 Most Common Marathon Training Mistakes
Preparing for a marathon isn't just about piling up kilometres. It's a long, demanding and very honest distance: if you arrive underprepared, if you've trained without structure or if you've confused consistency with excess, sooner or later the race gives it back to you.
The marathon doesn't forgive improvisation.
But there's no need to fear it either. With a well-planned preparation, enough rest, strength, strategy and a clear head, it can become one of the most powerful experiences any runner can have.
The problem is that many recreational runners make the same mistakes over and over. Some seem small during the build-up, but at kilometre 30 they turn into an enormous wall.
Here are the 10 most common mistakes when preparing for a marathon and, above all, how to avoid them. If you've got one of the autumn marathons on your calendar, like the Málaga Marathon, now is the time to go through them.
Preparing for the marathon with too little time
One of the most frequent mistakes is signing up for a marathon that's too close and thinking: "I'll build up the kilometres as I go".
Bad idea.
A marathon needs a base beforehand. Motivation, a good pair of shoes and a willingness to suffer aren't enough. To arrive properly prepared, ideally you come from a period in which you already run regularly and have absorbed a certain weekly volume.
Why it's a problem
If you start from a very low level and want to reach 42 km in a few weeks, what usually appears is:
- Overload.
- Niggles in the calves, soleus, knee or hip.
- Constant fatigue.
- Long runs you don't absorb properly.
- The feeling that you're forever "putting out fires".
How to avoid it
For a first marathon, a specific preparation of 16 to 20 weeks is usually reasonable, provided you already have a minimum base. If you're not yet comfortable running a 10K or a half marathon, the smart thing is to build that step first.
The marathon doesn't start on the day of your first long run. It starts months earlier, when you decide to prepare your body to tolerate the load.
Underestimating the distance
The marathon isn't "two half marathons". It's something else.
Up to kilometre 25 or 30 you can feel that everything is relatively under control. The problem is that the real race usually starts when you've already accumulated a lot of wear.
Why it's a mistake
Many runners arrive at the marathon thinking that, having done a half marathon, they just need to "hang on a bit longer". But in the marathon, factors come into play that matter less over shorter distances:
- Glycogen depletion.
- Accumulated muscle damage.
- Prolonged mental fatigue.
- Hydration and nutrition during the race.
- Managing your pace for more than 3, 4 or 5 hours.
How to avoid it
Respect the distance from the start.
That doesn't mean being afraid of it, but preparing for it seriously:
- Well-planned long runs.
- Realistic paces.
- Tested nutrition.
- Complementary strength work.
In a marathon, arriving with humility usually works better than arriving overconfident.
Running all your long runs too fast
The long run is a central piece of marathon training, but many runners turn it into a weekly competition.
Every Sunday they head out to prove they're strong. And of course, some weeks it goes well. But then come the niggles, the fatigue and the quality sessions done on dead legs.
Why it's a problem
The long run should build endurance, not destroy you.
If every long run ends as if you'd raced, you accumulate too much fatigue and reduce the quality of the rest of the week.
How to avoid it
Most long runs should be done at a comfortable, controlled pace, clearly below race pace. If you find it hard to identify that pace, learn to run by feel with RPE.
You can include some blocks at marathon pace in specific phases, but not always, not from the start and not every week.
A good long run should leave you tired, yes, but functional. It shouldn't force you to drag yourself around for three days.
Not training your race nutrition
In a 5K or 10K you can afford to improvise more. In a marathon, you can't.
Eating during the race is part of the training. If you don't practise gels, salts, water or isotonic drink before the big day, you're playing roulette.
Common mistakes
- Trying gels for the first time in the race.
- Taking fewer carbohydrates than you need.
- Drinking too late.
- Drinking a lot in one go.
- Not training your stomach.
- Thinking "I'll eat when I get hungry".
When you're hungry in a marathon, you're usually already too late.
How to avoid it
During your long runs, rehearse exactly what you'll do in the race:
- Which gel you'll take.
- How often.
- With how much water.
- Whether you'll use salts.
- Which breakfast sits well.
- What your stomach tolerates while running.
A common guideline for the marathon is to take carbohydrates regularly every 30 to 40 minutes, but it has to be adjusted to your tolerance, pace and expected finish time.
The rule is simple: nothing new on race day.
Neglecting strength
Many runners think that to run more, all you have to do is run more. Classic mistake.
Strength isn't a cosmetic extra. It's a tool for tolerating impact better, holding your technique when fatigue sets in and reducing the risk of injury.
What happens if you don't do strength work
As the kilometres go up, the body starts to show its weaknesses:
- Unstable hips.
- Knees that collapse inwards.
- Overloaded calves.
- Tight hamstrings.
- A loaded lower back.
- Technique that breaks down at the end of long runs.
How to avoid it
Include 1 or 2 strength sessions a week, especially in the first part of the preparation.
Prioritise:
- Squats.
- Lunges.
- Romanian deadlifts.
- Calf raises.
- Glute bridges or hip thrust.
- Anti-rotation core work.
- Foot and ankle work.
Hills are also a very specific form of strength for runners.
You don't need to become a weightlifter. You need to build a body capable of sustaining 42 km.
Doing too many hard days
Another typical mistake: intervals on Tuesday, hills on Thursday, a fast long run on Sunday and hard gym sessions in between.
That's not training better. That's accumulating stress.
Why it's dangerous
The body needs to alternate load and recovery. If every session is demanding, you never absorb anything.
The result is usually:
- Stagnation.
- Chronic fatigue.
- No spark in the legs.
- Recurring niggles.
- Poor performance in the important sessions.
How to avoid it
In marathon preparation, this is usually enough:
- 1 quality session a week.
- 1 long run.
- The rest, easy runs and complementary work.
There can be weeks with two demanding stimuli, but they need to be well placed and adapted to the runner's level.
My opinion is clear: many recreational runners don't fail because they train too little, they fail because they train too often at medium-high intensity. They live in a grey zone where they don't recover, but don't train real quality either.
Ignoring rest
Rest isn't what you do when you can't train. It's part of the plan.
If you train hard but sleep badly, eat too little and have no easy days, you're building on a fragile base.
Signs of poor recovery
- Easy runs that feel hard.
- A higher heart rate than normal.
- Heavy legs from the warm-up.
- Irritability.
- Poor sleep.
- Lack of motivation.
- Niggles that never quite go away.
How to avoid it
Plan your rest the same way you plan your intervals.
- 1 proper rest day a week can be very useful.
- Every 3 or 4 weeks, introduce a slightly easier week.
- After hard long runs, don't schedule quality too soon.
- Sleep as much as you can.
- Eat enough.
Resting doesn't make you lose fitness. It lets you show it.
Not having a clear pacing strategy
Setting off "by feel" can be fine if you have a lot of experience. But in a first marathon, starting without a strategy is usually a problem.
Marathon pace has to be realistic, not emotional.
Common mistake
Arriving at the start line with an idea like: "I'll try to run at 5:00/km and see what happens".
But if that pace isn't backed up by your training, the marathon will remind you.
How to avoid it
Define:
- Your target pace.
- A conservative pace.
- A plan for the first 10 km.
- What to do if it's hot or windy.
- What to do if you're already struggling at km 25.
- At what point you can start to push if you're feeling good.
A good strategy could be:
- Km 0 to 10: total control.
- Km 10 to 25: steady pace.
- Km 25 to 35: concentration and nutrition.
- Km 35 to 42: race with whatever is left.
The marathon is run with the legs, yes. But it's saved with the head.
Trying new things on race day
It sounds basic, but it keeps happening.
New shoes. New socks. New shirt. New gel. New breakfast. New belt. Forgotten Vaseline. Watch not set up.
In a marathon, any small detail can turn into a huge problem.
What can go wrong
- Chafing.
- Blisters.
- Stomach pain.
- A belt that bounces.
- A shirt that irritates.
- A sock that wrinkles.
- A gel you can't tolerate.
- A watch with no battery.
How to avoid it
Everything must be tested beforehand:
- Shoes with enough kilometres in them.
- Clothing worn on long runs.
- Rehearsed gels.
- A breakfast repeated several times.
- A tested hydration strategy.
- A watch that's set up.
Marathon day isn't for experimenting. It's for executing.
Preparing for the marathon alone without asking for help
You can prepare for a marathon on your own. Of course. A running group already gives you structure, company and motivation.
But if it's your first marathon, if you're coming back from injury or if you don't know how to organise load, paces, strength and rest, having professional help can make an enormous difference.
Why asking for help can be key
A professional can help you to:
- Set a realistic goal.
- Adjust your training paces.
- Place long runs and recovery weeks properly.
- Integrate strength without overdoing it.
- Prepare your nutrition and hydration.
- Avoid typical mistakes.
- Arrive on race day with fewer doubts.
A specialised team, like Cardenasports, can adapt the process to your level, your schedule, your history and your real goal.
Because the best plan isn't the hardest one. It's the one you can sustain, absorb and execute.
Bonus: signs you're on the right track
Not everything in the preparation has to feel epic. In fact, many good signs are fairly discreet:
- You finish your easy runs with something in reserve.
- Long runs tire you, but don't destroy you.
- You recover well between sessions.
- You have no persistent niggles.
- Your easy pace improves little by little.
- You know what to eat and drink in the race.
- You're clear on your target pace.
- You reach the final week wanting to run, not wanting it all to be over.
If your whole plan is based on surviving, something's wrong. If your plan lets you build week by week, you're doing fine. And if the nerves kick in during that last week, here's how to manage stress before a race.
Closing: the marathon rewards patience
The marathon is a special distance because it can't easily be fooled. It demands consistency, humility, strategy and the ability to listen to your body.
The most common mistakes usually aren't down to a lack of motivation, but to too much haste:
- Wanting to get there too fast.
- Training too hard.
- Resting too little.
- Setting off too bravely.
- Improvising too much on the big day.
Preparing well for a marathon isn't about suffering more than anyone else. It's about arriving on race day with the work done, the body ready and the head in the right place.
Because in the marathon, the epic part isn't wrecking yourself in training. The epic part is reaching kilometre 35 in one piece and still being able to run with purpose.
Train with patience. Recover with intelligence. Run with your head.